The top American general in Europe said the U.S. military does not yet have a plan to prevent Russia from building more nuclear-capable intermediate-range missiles once a treaty between Washington and Moscow banning the rockets ends in five months.

Army Gen. Curtis Scaparrotti told the Senate Armed Services Committee on Tuesday that the United States and its allies were still looking at options after the Trump administration withdrew from the Intermediate-Range Nuclear Forces Treaty on Feb. 1, triggering a six-month period before its formal dissolution.

“We in fact have told our allies in NATO that we will do this planning in collaboration with them. We have begun that. So, I don’t know that we have a plan today,” said Scaparrotti, supreme allied commander for Europe and head of the U.S. European Command. “I know that we are working on what we think that plan might be.”

Scaparrotti suggested that the United States should consider some sort of new or revived treaty with Russia to set limits and create stability.

“From my point of view, when you have a peer competitor, and particularly a modernizing one that will be challenging you, such as Russia, we should look toward treaty capabilities in order to provide some stability, to provide signals and communications and limits that we understand and that we can work from,” he said.

Russia is not challenging the United States in Europe only in the nuclear space. Moscow has brokered a deal to provide Turkey with an S-400 missile-defense system, provoking ire in Washington by making inroads with a U.S. NATO ally. Scaparrotti said Tuesday that the United States should withhold the F-35 fighter jet from Turkey as long as Ankara proceeds with buying antiaircraft systems from Russia.

The issue is part of a broader standoff with Russia in Europe, with the INF Treaty the latest flash point.

Signed by President Ronald Reagan and Soviet leader Mikhail Gorbachev in 1987, the treaty banned the production, deployment and testing of nuclear and conventional ground-launch missiles with ranges between 500 and 5,500 kilometers (311 and 3,418 miles).

The United States pulled out of the treaty last month, alleging violations by Russia that included the deployment of the Novator 9M729, a ground-launch cruise missile that Washington warned was contravening the treaty. Russia denied the accusations and in turn accused the United States of violating the pact with missile defense installations — an allegation the State Department rejected.

Led by White House national security adviser John Bolton, the White House withdrew from the treaty not only because Russia was violating the pact but also because China, which is not a party to it, has been producing intermediate-range missiles the U.S. military wants to counterbalance in Asia.

On Monday, Russian President Vladi­mir Putin responded to the Trump administration’s withdrawal from the INF Treaty by formally suspending Moscow’s participation. Putin has warned that Russia will be forced to take reciprocal measures if the United States puts more missiles in Europe, raising concerns about a new missile race on the continent similar to the one that led to the INF Treaty in the first place in the 1980s.

The Trump administration, upon pulling out of the treaty, said it was not considering deploying any new nuclear missiles in Europe as a result of the pact’s breakdown.

The White House is considering whether to renew the New START accord with Russia, which limits strategic nuclear arms and is the last remaining substantive arms-control pact linking Washington and Moscow. Negotiated by President Barack Obama, the treaty expires in less than two years but contains an automatic extension clause should the presidents of both nations agree.

If New START is not extended, the world will return to an era without any legally binding or verifiable limits on its two biggest nuclear powers for the first time since 1972.